1. Field of the Invention
The present invention relates to a method of manufacturing a multilayered disk capable of refraining from an interlayer interference between adjacent layers when a specific layer of the multilayered layers is recorded or regenerated in an optical disk.
2. Background of the Related Art
As a request for high quality moving pictures is increased in accordance with an improvement of consumers' lifestyle along with a speed doubling and an increase of storing density of an optical storing device, a larger volume of storing data of an optical storing disk is required.
FIG. 1 is a schematic block diagram of a general optical pickup device.
Referring to FIG. 1, the optical pickup device comprises a laser diode 101 emitting a beam with a regular wavelength, a beam splitter 102 reflecting or transmitting the beam, a collimator lens 103 emitting the beam impinged from the beam splitter 102 into a parallelized beam, an object lens 104 condensing the beam impinged from the collimator lens 103 to the optical disk 105 and transmitting the reflected beam to the collimator lens 103 and a photo detector 106 detecting the beam reflected by the beam splitter 102 and emitting it as an electric signal.
The above configured optical pickup device is shown in FIG. 1. As shown in FIG. 1, a laser beam emitted from the laser diode LD 101 is transmitted through the beam splitter 102 and the transmitted beam is impinged to an object lens 104 from the collimator lens 103 as a parallel beam. The object lens 104 condenses an impinged beam to a point on the optical disk 105 to record and regenerate the information, and a beam formed from the optical disk 105 is reflected. The reflected beam is transmitted through the object lens 104 and the collimator lens 103 to be reflected to the photo detector 106 by the beam splitter 102. The photo detector 106 changes the information which is reflected and input into an electric signal.
In a recent optical system, a lot of methods are attempted in order to increase a recording volume of an optical disk. A representative method is to increase a recording density by decreasing the size of a light condensed on a disk. The object can be obtained by decreasing a wavelength of a laser and increasing a numerical aperture of the object lens for condensing a light.
The recently developed recording and regenerating device of an optical disk for Blu-ray Disk BD employs a laser wavelength of 450 nm and a numerical aperture of the object lens of 0.85 to have a recording volume of 25 GB per one disk of 12 cm.
In addition, researches on a method using a UV laser with a shorter wavelength or a method for recording a near field for further widening a numerical aperture of an object lens have been carried out in order to further increase a recording volume.
As another method for increasing the total recording volume in the process, the number of recording layers is increased by making the recording layer of an optical disk have multiple layers, with maintaining the two dimensional recording densities.
FIG. 2 schematically shows a Blu-ray disk where the dual layers are formed and a pickup device thereof.
Referring to FIG. 2, the Blu-ray disk 30 is formed to have two recording layers 1 and 2 with a predetermined distance d2 therebetween. The recording layer 1 is formed in the same direction of the object lens 11 of an optical pickup with a predetermined distance d1.
An optical disk device for reading or recording the recorded data onto a recording layer of the Blu-ray disk 30 is variably controlled to be suitable for recording or regenerating a laser power of a laser diode LD 13 included in the pickup. For example, the optical pickup performs the operations of recording or regenerating by transforming a light source emitted from the laser diode 13 into a parallelized light in the collimator lens CL 12, and condensing the parallelized light on the recording layer of a disk in the object lens OL 11 and reflecting it again.
As described above, in the case of DVD or BD disks, a method for increasing a recording volume using two layers has been already completed, and a method for increasing a recording layer of a BD disk to have six or eight layers or further is developed.
However, the most serious problem of the above described multilayered disk is that a light reflected from an undesired layer is received to a photo detector to operate as a noise when a laser light is condensed on a layer to be recorded or regenerated. Thus, it is required to adjust a shape of a photo detector and a range of a reflective signal or S-curve range and so on in order to decrease the noise.